1. Field of the Invention
The present invention relates to an optical lens. More particularly, the present invention relates to an optical lens capable of forming a desired distribution of illumination intensity.
2. Description of Related Art
Having the advantage of saving energy, light emitting diodes (LEDs) are gradually replacing the traditional lamp bulbs and used as the next generation light sources for general lighting applications, which include indoor and outdoor lightings. However, in practical use, since the dimensions of a single LED chip are extremely small, the light intensity can be quite high within an adjacent small area around the LED chip. That may cause discomfort to the human eye when directly viewing the LED chip.
Therefore, in practical applications, at least one optical element is often provided onto the LED chip for improving the uniform illumination and solving the above-mentioned problem of ultra-high light intensity area around the LED chip. In some particular applications, the optical element can further be designed in shape and size to adjust the distribution of illuminating intensity.
As to the applications of street lamps, the light emitted from street lamps illuminate road surfaces at night for vehicle drivers to have clear sights and ensure the driving safety. Therefore, the street lamps are often required to provide a better uniformity of the illumination distribution on the roads. The street lamps are usually arranged at intervals along the roadside and each of them has a lamp post standing on the ground and a lamp holder at the top end of the lamp post. The lamp holder should be set inclined upwardly in order to illuminate toward the middle of the road for providing better uniformity of the illumination distribution. However, such a configuration may lead to a negative influence. The upwardly inclined lamp holder may increase the possibility that the light source in the lamp holder may be directly viewed by the human eye thus cause discomfort and blurred vision. And the above-mentioned situation will be worse when the LEDs are used as light sources in the street lamps, since the light intensity around the LED chip is higher than other conventional light sources.